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help for dsginideco                        Jenkins and Van Kerm (February 2009)
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Decomposition of inequality change into pro-poor growth and mobility components


    dsginideco var0 var1 [weight] [if exp] [in range] [, parameters(numlist)
              format(%fmt) percentage percformat(%fmt) kakwani ]

    aweights and fweights are allowed; see help weights.

    dsginideco requires panel data, in wide form, on income in two time
    periods.  var0 contains the measure of income in the initial period for
    each observation.  var1 contains the measure of income in the final
    period for each observation.  If the data are held in long form,
    time-series operators may be used to define var0 or var1: see the
    Examples.


Description

    dsginideco decomposes the change in income inequality between two time
    periods into two components, one representing the progressivity
    (pro-poorness) of income growth, and the other representing reranking.
    Inequality is measured using the generalized Gini coefficient, also known
    as the S-Gini, G(v). This is a distributionally-sensitive inequality
    index, with larger values of v placing greater weight on inequality
    differences among poorer (lower ranked) observations. The conventional
    Gini coefficient corresponds to the case v = 2. The decomposition is of
    the form:

        final-period inequality - initial-period inequality = R - P

    where R is a measure of reranking, and P is a measure of the
    progressivity of income growth.

    For full details of the decomposition and an application, see Jenkins and
    Van Kerm (2006).  For an application to the related topic of
    cross-country convergence, see O'Neill and Van Kerm (2008).

    See the online manual for additional discussion and examples.


Options

    parameters(numlist) specifies a value or values for v in G(v). The
        default value is 2, leading to a decomposition of the standard Gini
        coefficient. Multiple values of v can be given but every value
        specified must be greater than 1.

    format(string) specifies a format for the displayed results.  The default
        is %5.3f.

    percentage requests that decomposition factors be reported as fractions
        of the initial-period G(v).

    percformat(string) used in conjunction with percentage specifies a format
        for results expressed as a fraction of base-period Gini.  The default
        is %4.1f.

    kakwani requests reporting of the Kakwani-type measure of progressivity
        of income growth, K. (See Jenkins and Van Kerm 2006 for the
        definition.) This statistic is meaningful only when average income
        growth is not close to zero.


Saved Results

    Scalars:

    r(sgini0)        G(v) for initial period incomes

    r(sgini1)        G(v) for final period incomes

    r(dsgini)        Change in inequality: final-period G(v) - initial-period
                 G(v)

    r(pi)            Average income growth between initial and final period

    r(P)             P

    r(R)             R

    r(K)             K, if requested

    r(N)             Number of observations

    r(sum_w)         Sum of weights

    Macros:

    r(var0)          The name of variable var0

    r(var1)          The name of variable var1

    r(paramlist)     The value(s) of v

    Matrices:

    r(coeffs)        All estimates: G(v) for both periods, the change in
                 G(v), P and R, and K if requested

    r(parameters)    Vector containing the value(s) of v

    When the percentage option is specified, an additional set of results is
    returned, each prefixed by rel, containing the estimates expressed as a
    fraction of the initial-period G(v). Type return list after dsginideco to
    find out exactly what results are returned.


Examples

        . use http://www.stata-press.com/data/r9/nlswork , clear

        . tsset idcode year

        . gen w = exp(ln_wage)

        . dsginideco L.w w

        . dsginideco L.w w , percentage parameters(1.5 2 3 4) kakwani

        . gen newid = idcode

        . tsset newid year

        . bootstrap dG=r(dsgini) R=r(R) P=r(P) ///

              , cluster(idcode) idcluster(newid) reps(250) nodots: ///

              dsginideco L.w w if !mi(L.w) & !mi(w)

        . jackknife dG=r(dsgini) R=r(R) P=r(P) ///

              , cluster(idcode) idcluster(newid) rclass nodots: ///

              dsginideco L.w w if !mi(L.w) & !mi(w)


References

    Jenkins, S.P. and Van Kerm, P. (2006). Trends in income inequality,
        pro-poor income growth and income mobility. Oxford Economic Papers,
        58(3): 531-548. [link]

    O'Neill, D. and Van Kerm, P. (2008). An integrated framework for
        analysing income convergence.  The Manchester School. 76(1): 1-20.
        [link]


Authors


   Stephen P. Jenkins
   ISER, University of Essex, UK
   
   Philippe Van Kerm
   CEPS/INSTEAD, Luxembourg
   philippe.vankerm@ceps.lu